Resolving ECMAScript Module Import Errors in TypeScript: A Guide to esModuleInterop

Learn how to resolve errors related to ECMAScript imports/exports in TypeScript, including the `esModuleInterop` flag, while developing an API testing framework.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding esModuleInterop in TypeScript

When working with TypeScript, particularly in modern web development, you may encounter challenges related to importing and exporting modules. Such issues can arise, especially if you're transitioning from CommonJS modules to ECMAScript modules (ESM). One common error that developers face is:
"This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export."

In this guide, we will delve into this error, provide context on esModuleInterop, and guide you through an effective solution for using imports in your API testing framework built with TypeScript.

Breaking Down the Problem

[[See Video to Reveal this Text or Code Snippet]]

You then attempt to import this helper in your spec file like so:

[[See Video to Reveal this Text or Code Snippet]]

However, when you run your tests, you receive an error that suggests an issue with how you're exporting or importing modules.

Why Does This Happen?

The error occurs due to the way TypeScript handles module exports. The export = syntax creates a CommonJS-style module which, under certain conditions, requires you to import it in a specific way. If you're using ECMAScript syntax (import) instead, TypeScript needs some configuration adjustments.

The Solution: Switching Export Syntax

Step-by-Step Solution

[[See Video to Reveal this Text or Code Snippet]]

To:

[[See Video to Reveal this Text or Code Snippet]]

How This Works:

The first method (export =) is mainly meant for compatibility with CommonJS modules. If you go this route, you'll need to import using import assertions from './assertions'.

The second method allows you to use modern ES module syntax. Now, you can import your assertion function in several ways:

import { assertSuccessResponseStatusCode } from './assertions'

import * as assertions from './assertions'

Advantages: This change not only resolves the module import error but also allows you to combine default exports with named exports in the future. This flexibility can be very beneficial as your API testing framework grows.

Conclusion

Transitioning to TypeScript and navigating through its import/export nuances can be challenging at first. However, understanding the intricacies of modules, particularly within the context of the esModuleInterop flag, can help alleviate many of these issues. By simply adjusting your export syntax as discussed, you can seamlessly import your helper functions without encountering module-related errors.

Next time you run into this error, remember that a small change in syntax could save you a lot of debugging time. Happy coding!